The present invention relates to a high-intensity discharge lamp lighting apparatus for stably lighting a high-intensity discharge lamp and to a luminaire for using the same.
Conventionally, such a discharge lamp lighting apparatus is disclosed in the JP 62-241295.
The discharge lamp lighting apparatus disclosed in the JP62-241295 is provided with an LC resonance type electronic ballast for preheating filaments in discharge lamps.
The electronic ballast makes its frequency to continuously lower in beginning with a frequency higher than an LC resonance frequency. When the frequency becomes close to the LC resonance frequency, the lamps having filaments are started up into a lighting state. When the electronic ballast starts an oscillation at such a high frequency, the filaments are preheated by a low secondary voltage enough to avoid a start-up of the discharge lamp. As the electronic ballast frequency gradually lowers and becomes close to the LC resonance frequency, the secondary voltage is boosted. When the secondary voltage reaches a predetermined voltage, the discharge lamp is started up. After a discharge lamp has lighted up, the electronic ballast frequency lowers below the LC resonance frequency. Then the discharge lamp is maintained in lighting state.
However, the discharge lamp lighting apparatus disclosed in the JP62-241295 has drawbacks of complicated operation and control for varying the secondary voltage by continuously varying the frequency. In a low pressure discharge lamp such as a fluorescent lamp, the discharge lamp is started up into a lighting state when the secondary voltage becomes a high voltage for a very short period even shorter than a second. However, in a high-intensity discharge lamp, especially using a neon (Ne) and an argon (Ar), the secondary voltage must be maintained for a relatively long period, i.e., one to two seconds for the glow-arc transition. However, in the conventional discharge lamp, it was unable to maintain the high voltage comparatively for a long time. So that, it was difficult to start to light the high intensity discharge lamp certainly.
On the other hand, the electronic ballast needs a frequency of 20 kHz or more that is the upper limit of an audible frequency range in order to prevent flickering. Moreover, it is common to set the electronic ballast frequency to 100 kHz or less in order to make measures against the flickering easy. However, in the band of 20 kHz to 100 kHz, which is used relatively often for the electronic ballast frequency, there exist dispersively several frequency bands wherein the high intensity discharge lamp might causes acoustic resonance. Thus, a frequency around the central region of the stable operation window, that is a frequency band free from acoustic resonance, among areas where the acoustic resonance might occur on the high-intensity discharge lamp, is used for the electronic ballast resonance frequency.
However, since the frequency band of this stable operation window is very narrow, when the electronic ballast frequency is being fixed, several frequency bands of acoustic resonance of the high intensity discharge lamps overlap the fixed electronic ballast frequency according to variations in products, so as to cause the drawback of acoustic resonance, i.e., flickering. In such a case, it is difficult to determine in which end of the fixed electronic ballast frequency band the acoustic resonance occurs. That is, it is difficult to determine whether the acoustic resonance occurs in the upper end of a lower frequency band or in the lower end of a higher frequency band. Therefore, it is difficult to deal with the acoustic resonance.
To solve such problems, it is considered to choose the electronic ballast frequency in a sufficiently high frequency band or in a sufficiently low frequency band which is free from acoustic resonance.
However, in such a high frequency, there is a drawback that the switching loss of the electronic ballast becomes large.
Further, for obtaining such a low frequency, the inductance of an LC resonance circuit has to be made larger. As a result, there is a drawback of upsizing a coil constituting the LC resonance circuit.
As described above, in the discharge lamp lighting apparatus disclosed in the JP62-241295, the control of varying the secondary voltage in the operation of continuously varying the electronic ballast frequency becomes complicated.
Moreover, in the case of a high intensity discharge lamp, it is required to maintain a high no-load voltage for 1 or 2 seconds for causing the glow-arc transition. However, it is difficult to continuously vary the frequency while fulfilling such conditions. Thus it is also difficult to maintain the open circuit voltage for a sufficient time.
Furthermore, if it is tried to use the central frequency in a stable operation window of a very narrow frequency band within the frequency band of 20 kHz to 100 kHz that is used very often as an electronic ballast oscillation frequency, an actual oscillation frequency deviates from the stable operation window. Accordingly, since it is unclear whether the oscillation frequency is higher or lower than the stable operation window even when the lamp power varies extensively, or the acoustic resonance occurs, it is difficult to deal with these problems. When the electronic ballast oscillation frequency rises to a high frequency enough for avoiding acoustic resonance, there occurs a problem of increasing the switching loss. On the contrary, however when the electronic ballast oscillation frequency lowers to a low frequency enough for avoiding acoustic resonance, there occurs another problem of upsizing the apparatus.
The present invention was made in view of these problems, and it has an object to provide a high-intensity discharge lamp lighting apparatus for stably lighting a high-intensity discharge lamp and a luminaire for using the same.
In order to achieve the object described above, the high-intensity discharge lamp lighting apparatus according to the first embodiment of the present invention, comprising, a main circuit which contains an LC resonance circuit, and which is coupled to a high-intensity discharge lamp, an electronic ballast which starts and lights the high-intensity discharge lamp via the main circuit which is coupled to the output side of it, and which is operated with a resonance frequency of the LC resonance circuit in the main circuit in the no-load condition, and the electronic ballast, which is operated at the resonance frequency of the LC resonance circuit in the main circuit in the no-load condition, can increase a secondary open voltage through the glow discharge condition and maintain the high secondary voltage at the time of glow-arc transition.
The high-intensity discharge lamp lighting apparatus according to a second embodiment of the present invention, the LC resonance circuit is provided with inductors in addition. The inductors saturate at the start of the glow discharge of the high-intensity discharge lamp, and fail to saturate during the glow discharge and arc discharge operations. A high intensity discharge lamp starts the glow discharge operation in a short time by applied the high voltage since it requires the electrical breakdown before lighting, and it applies less stress to a circuit even under the condition that the inductors saturate. As it is necessary to radiate thermions in a glow-arc transition, it is able to avoid stresses being applied to the circuit if the circuit is maintained in a relatively high voltage for a period necessary for the glow-arc transition by avoiding saturation of inductors.
A high-intensity discharge lamp lighting apparatus according to a third embodiment of the present invention, wherein the operating frequency of the electronic ballast at the start of the glow discharge of the high-intensity discharge lamp matches the resonance frequency of the LC resonance circuit in the no-load condition under the state that the inductors saturate, and its frequency during the glow discharge of the high-intensity discharge lamp matches the no-load resonance frequency of the LC resonance circuit under that state that the inductors fail to saturate. So, it becomes easy to control the frequencies of the high-intensity discharge lamp at the start of the glow discharge time, during the glow discharge, and at the glow-arc transition time. Accordingly, even in the high intensity discharge lamp which requires a high voltage to maintain the glow discharge (a high intensity discharge lamp in which Ne is filled), it is able to maintain the glow discharge and improve the start-up performance. Here, the no-load resonance frequency during a glow discharge operation and at a glow-arc transition means an acoustic resonance frequency of the whole including the high intensity discharge lamp. Since the high-intensity discharge lamp during the glow discharge operation and at the glow-arc transition time is in a high impedance state, they are indicated as a no-load here.
A high-intensity discharge lamp lighting apparatus according to a fourth aspect of the present invention further comprises, a glow discharge detector for detecting the glow discharge of the high intensity discharge lamp, and an output reducer for reducing an output voltage within the range where the glow discharge is maintained at a frequency higher than the resonance frequency at the no-load state of the LC resonance circuit under the condition where the inductors are not saturate after detecting the glow discharge in the glow discharge detector, wherein after the detection of the glow discharge, the electronic ballast is effectively operated at a lagging phase and a frequency higher than the resonance frequency at the no-load state, while its output voltage lowers. Accordingly, it is able to reduce the voltage inputted to the high-intensity discharge lamp at the glow discharge time, and suppress a blackening of the lamp by suppressing sputtering of electrode materials in high-intensity discharge lamps.
A high-intensity discharge lamp lighting apparatus according to a fifth aspect of the present invention, wherein the operating frequency of the electronic ballast is set to be near the upper limit or the lower limit of the frequency band where the acoustic resonance occurs on the high-intensity discharge lamp. So, even when the acoustic resonance occurs on the high-intensity discharge lamp, it is easy to determine whether the lighting frequency is too high or too low. Thus, by controlling the lighting frequency to be shifted into either frequency band which is free from acoustic resonance, so as to avoid the acoustic resonance.
A high-intensity discharge lamp lighting apparatus according to a sixth aspect of the present invention, further comprising an acoustic resonance detector for detecting the acoustic resonance of the high-intensity discharge lamp. When the acoustic resonance is detected in the acoustic resonance detector, the operating frequency of the electronic ballast shifts into either frequency band which is free from acoustic resonance. As the acoustic resonance is reduced if the electronic ballast frequency shifts into either frequency band which is free from acoustic resonance, and is opposite to the frequency band close to the ordinary set-up frequency where the acoustic resonance might occur, the acoustic resonance is avoided by shifting the frequency to the other end of the frequency band which is free from acoustic resonance.
A high intensity discharge lamp lighting apparatus according to a seventh aspect of the present invention comprises a timer circuit in addition. When the glow discharge detector does not detect the glow discharge of the discharge lamp within a specific periods clocked with the timer circuit, the electronic ballast is reset to the state at the start of operation. When the discharge lamp fails the glow discharge, the operation is repeated from the state at the start of operation.
A luminaire according to an eighth aspect of the present invention comprises a high-intensity discharge lamp lighting apparatus of any embodiments described above, and a lighting equipment main body whereon the high-intensity discharge lamp to be lighted up in the high-intensity discharge lamp lighting apparatus is mounted.
Additional objects and advantages of the present invention will be apparent to persons skilled in the art from a study of the following description and the accompanying drawings, which are hereby incorporated in and constitute a part of this specification.